feature #386 Added support for OAuth 2.0 PKCE (MLukman)

This PR was squashed before being merged into the master branch.

Discussion
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Added support for OAuth 2.0 PKCE

Added OAuth2PKCEClient that supports OAuth 2.0 providers with PKCE extension (https://oauth.net/2/pkce/)

Commits
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571b4fc Added support for OAuth 2.0 PKCE

src/Client/OAuth2PKCEClient.php

@@ -0,0 +1,95 @@
+<?php
+
+/*
+ * OAuth2 Client Bundle
+ * Copyright (c) KnpUniversity <http://knpuniversity.com/>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace KnpU\OAuth2ClientBundle\Client;
+
+use League\OAuth2\Client\Provider\AbstractProvider;
+use League\OAuth2\Client\Token\AccessToken;
+use League\OAuth2\Client\Token\AccessTokenInterface;
+use LogicException;
+use Symfony\Component\HttpFoundation\Exception\SessionNotFoundException;
+use Symfony\Component\HttpFoundation\RedirectResponse;
+use Symfony\Component\HttpFoundation\RequestStack;
+use Symfony\Component\HttpFoundation\Session\SessionInterface;
+
+/**
+ * Subclass of OAuth2Client for handling OAuth 2.0 providers using PKCE extension (https://oauth.net/2/pkce/).
+ *
+ * @author Muhammad Lukman Nasaruddin (https://github.com/MLukman/)
+ */
+class OAuth2PKCEClient extends OAuth2Client
+{
+    public const VERIFIER_KEY = 'pkce_code_verifier';
+
+    /** @var RequestStack */
+    private $requestStack;
+
+    public function __construct(AbstractProvider $provider,
+                                RequestStack $requestStack)
+    {
+        parent::__construct($provider, $requestStack);
+        $this->requestStack = $requestStack;
+    }
+
+    /**
+     * Enhance the RedirectResponse prepared by OAuth2Client::redirect() with
+     * PKCE code challenge and code challenge method parameters.
+     *
+     * @see OAuth2Client::redirect()
+     * @param array $scopes
+     * @param array $options
+     * @return RedirectResponse
+     */
+    public function redirect(array $scopes = [], array $options = [])
+    {
+        $this->getSession()->set(static::VERIFIER_KEY, $code_verifier = bin2hex(random_bytes(64)));
+        $pkce = [
+            'code_challenge' => rtrim(strtr(base64_encode(hash('sha256', $code_verifier, true)), '+/', '-_'), '='),
+            'code_challenge_method' => 'S256',
+        ];
+
+        return parent::redirect($scopes, $options + $pkce);
+    }
+
+    /**
+     * Enhance the token exchange calls by OAuth2Client::getAccessToken() with
+     * PKCE code verifier parameter
+     *
+     * @see OAuth2Client::getAccessToken()
+     * @param array $options
+     * @return AccessToken|AccessTokenInterface
+     * @throws LogicException When there is no code verifier found in the session
+     */
+    public function getAccessToken(array $options = [])
+    {
+        if (!$this->getSession()->has(static::VERIFIER_KEY)) {
+            throw new LogicException('Unable to fetch token from OAuth2 server because there is no PKCE code verifier stored in the session');
+        }
+        $pkce = ['code_verifier' => $this->getSession()->get(static::VERIFIER_KEY)];
+        $this->getSession()->remove(static::VERIFIER_KEY);
+        return parent::getAccessToken($options + $pkce);
+    }
+
+    /**
+     * @return SessionInterface
+     * @throws LogicException When there is no current request
+     * @throws SessionNotFoundException When session is not set properly [thrown by Request::getSession()]
+     */
+    protected function getSession()
+    {
+        $request = $this->requestStack->getCurrentRequest();
+
+        if (!$request) {
+            throw new LogicException('There is no "current request", and it is needed to perform this action');
+        }
+
+        return $request->getSession();
+    }
+}

tests/Client/OAuth2PKCEClientTest.php

@@ -0,0 +1,117 @@
+<?php
+
+/*
+ * OAuth2 Client Bundle
+ * Copyright (c) KnpUniversity <http://knpuniversity.com/>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace KnpU\OAuth2ClientBundle\tests\Client;
+
+use KnpU\OAuth2ClientBundle\Client\OAuth2PKCEClient;
+use League\OAuth2\Client\Provider\AbstractProvider;
+use League\OAuth2\Client\Provider\ResourceOwnerInterface;
+use League\OAuth2\Client\Token\AccessToken;
+use PHPUnit\Framework\TestCase;
+use Psr\Http\Message\ResponseInterface;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\RequestStack;
+use Symfony\Component\HttpFoundation\Session\Session;
+use Symfony\Component\HttpFoundation\Session\Storage\MockArraySessionStorage;
+
+class OAuth2PKCEClientTest extends TestCase
+{
+    private $requestStack;
+    private $session;
+    private $provider;
+
+    public function setup(): void
+    {
+        $this->session = new Session(new MockArraySessionStorage());
+        $this->request = new Request();
+        $this->request->setSession($this->session);
+        $this->requestStack = new RequestStack();
+        $this->requestStack->push($this->request);
+        $this->provider = new class extends AbstractProvider {
+
+            protected function checkResponse(ResponseInterface $response, $data): void
+            {
+                // not needed
+            }
+
+            protected function createResourceOwner(array $response,
+                                                   AccessToken $token): ResourceOwnerInterface
+            {
+                // not needed
+            }
+
+            protected function getDefaultScopes(): array
+            {
+                return [];
+            }
+
+            public function getBaseAccessTokenUrl(array $params): string
+            {
+                // not needed
+            }
+
+            public function getBaseAuthorizationUrl(): string
+            {
+                return 'http://coolOAuthServer.com/authorize';
+            }
+
+            public function getResourceOwnerDetailsUrl(AccessToken $token): string
+            {
+                // not needed
+            }
+
+            public function getAccessToken($grant, array $options = [])
+            {
+                // hijack this method to just create a new AccessToken using the $options
+                return new AccessToken($options + ['access_token' => 'DUMMY_ACCESS_TOKEN']);
+            }
+        };
+    }
+
+    public function testRedirect()
+    {
+        $client = new OAuth2PKCEClient(
+            $this->provider,
+            $this->requestStack
+        );
+        $client->setAsStateless();
+
+        $response = $client->redirect();
+        $this->assertInstanceOf(
+            'Symfony\Component\HttpFoundation\RedirectResponse',
+            $response
+        );
+
+        // assert the code_challenge & code_challenge_method parameters are in the redirect response
+        $queries = [];
+        parse_str(parse_url($response->getTargetUrl(), PHP_URL_QUERY), $queries);
+        $this->assertArrayHasKey('code_challenge', $queries);
+        $this->assertArrayHasKey('code_challenge_method', $queries);
+    }
+
+    public function testGetAccessToken()
+    {
+        $client = new OAuth2PKCEClient(
+            $this->provider,
+            $this->requestStack
+        );
+        // skip state checking
+        $client->setAsStateless();
+
+        // ensure code verifier is generated by redirect() and stored in session first
+        $client->redirect();
+        // OAuth2Client::getAccessToken() requires 'code' query parameter
+        $this->request->query->set('code', 'DUMMY_CODE');
+
+        // assert the code_verifier parameter is passed and returned back by the hijacked provider
+        $accessToken = $client->getAccessToken();
+        $this->assertArrayHasKey('code_verifier', $accessToken->getValues());
+    }
+}